In a vehicle equipped with an internal combustion engine, evaporative fuel control canister type devices are used for controlling loss of fuel vapor from fuel tanks and fuel-dispensing units such as carburetors. A common canister device containing a quantity of fuel-absorbing materials such as activated charcoal is connected to the fuel tank vents and the fuel-dispensing unit vents which stores the fuel vapor emitted therefrom. During vehicle operation, the fuel vapor stored is purged from the fuel-absorbing material back into the engine induction system.
Activated charcoal has been found a suitable fuel vapor absorbing material to be used in such a canister device because of its very large surface area to weight ratio, i.e., the particles of activated charcoal are extremely porous and have a sponge-like structure. This open porous structure while extremely effective in the absorption of fuel vapor can be blocked and loses its efficiency when coated with liquid fuel. This occurs when liquid fuel is accidentally spilled into the fuel vapor inlet of a canister device. The term liquid fuel is used to include liquid gasoline and other high molecular weight hydrocarbons with six or more carbon atoms such as benzene, toluene, heptane, and xylene.
It is therefore an object of the present invention to provide an evaporative fuel vapor control canister device containing a quantity of fuel vapor absorbing material having improved fuel vapor absorbing capability.
It is another object of the present invention to provide an evaporative fuel vapor control canister device containing fuel absorbing materials having not only excellent fuel vapor absorption capability but also excellent liquid fuel absorption capability.